Those interested in participating are required to sign into the the official Battlefield Heroes website with their EA Account, and must then proceed to the sign-up form.

Those who have participated in past Battlefield Heroes beta tests are automatically signed up for the next phase, and do not need to enter. It was not said when the next phase will begin, though DICE noted that more players will gain access over time.

The last round of beta testing concluded on November 14, 2008. The free-to-play game, which relies on microtransactions and out-of-game ads for financial support, was originally slated to arrive last summer, then late 2008, and is now expected this year.

Thanks to Luckyg for the tip.